YOU'VE maybe heard about " W. ," Ol iver Stone 's tough feature film about Bush. Stone calls him "horrible . . . worst in history." Josh Bro lin plays W.; Elizabeth Banks Laura James Cromwell , papa Bush Ellen Burstyn , mama Barbara Thandie Newton Condoleezza . First-ever movie about a sitting president, shooting in Shreveport, La., is so hush-hush secret that all scripts are embargoed. Watermarked so that each is traceable. So do not ask - do not - how one is now in my own sticky fingers. Do not ask. If I answered, which I won't, I'd have to lie. A supposed chronicle of his presidency, every scene or shard of dialogue is theoretically - if not proven fact - within the realm of repeated rumor. No imaginary scenes off the deep end. Stone's trying for legitimacy so he won't get pilloried. Or